The present invention relates in general to a device for the lengthwise cutting of a weblike material, such as, for example and in particular, corrugated cardboard, which is subdivided into a plurality of strips having a desired width, from which individual sheets having the desired dimensions are then produced by means of transverse cuts.
In cutting and creasing plants for the production of sheets of corrugated cardboard intended, for example, for the manufacture of boxes, it frequently becomes necessary to change the job being processed. The job change normally requires a change in the positions of the lengthwise cutting lines and/or of the lengthwise creasing lines. This occurs because different jobs performed in succession by the same plant are characterized by different dimensions of the final sheets produced.
During the job change phase, certain problems arise that are well known to those skilled in the art, in particular when the plant is of the type having two or more levels, in other words of the type in which the strips cut lengthwise from a single weblike material are conveyed to transverse cutting devices disposed at different heights. In this case, one of the lengthwise cutting lines subdivides the weblike material into one or more strips that are conveyed to a first level and one or more strips that are conveyed to a different level to be subdivided into sheets. On the occasion of a job change, the intermediate cutting line that subdivides the strips being conveyed to the two levels is normally shifted in position, so that it becomes necessary to connect the two intermediate cutting lines in order to avoid the tearing of the weblike material.
The problems associated with plants of this type, in particular in relation to job changes, and the respective solutions proposed are described in detail in EP-B-0 737 553 and in the patents cited therein, to which reference is made for a more thorough analysis. A different solution to the abovementioned problem is described in EP-A-0 894 583.
It is the object of the present invention to propose a method and a device that make it possible to overcome the problems of job changes in multilevel cutting and creasing plants.
Substantially, according to the invention, a device is provided comprising a plurality of lengthwise cutting tools and one transverse cutting tool, wherein the lengthwise cutting tools are controlled in a manner such as to generate a first series of lengthwise cutting lines in a first working job and a second series of lengthwise cutting lines in a second working job, a transition zone from the first to the second job being generated between the two working jobs wherein said transverse cutting tool generates a transverse connecting cut. According to the invention, the device is characterized in that it comprises at least one auxiliary lengthwise cutting tool which, in said transition zone, generates an auxiliary lengthwise cut which is joined, via the transverse cut, to one of the lengthwise cutting lines generated by said lengthwise cutting tools, or to a second auxiliary lengthwise cut generated by a second auxiliary lengthwise cutting tool.
The transverse connecting cut may be orthogonal to the direction of advance of the weblike material, but this is not absolutely necessary. The term transverse cut is to be generally understood as meaning, in the present context, a cut that is not parallel to the direction of advance of the weblike material.
According to a practical embodiment of the invention, the auxiliary lengthwise cutting tool is controlled in a manner such as to generate within the transition zone between the two jobs the auxiliary lengthwise cut aligned with and joined to one of the lengthwise cutting lines of the first job. The lengthwise cutting tools are controlled in a manner such that one of the lengthwise cutting tools intended to cut the weblike material lengthwise in the second job is brought into a working position in advance, relative to the remaining tools, to generate a lengthwise cutting line which is joined by the transverse cut to said auxiliary lengthwise cut in the transition zone between the two successive jobs.
By means of the device according to the present invention it is possible to implement a method for cutting an indefinite weblike material lengthwise into a plurality of lengthwise strips, comprising the phases of:
subdividing said weblike material into a plurality of strips as required by a first working job by lengthwise cutting lines generated by lengthwise cutting tools;
on completion of the processing of said first job, changing the position of the cutting tools and commencing the processing of a second job with a different positioning of lengthwise cutting lines, generating a transition zone between the end of the first job and the start of the second job;
connecting two lengthwise cutting lines of the first and second jobs in said transition zone between the first and the second job by means of a transverse cut;
generating in said transition zone between the two successive jobs, by means of an auxiliary lengthwise cutting tool, an auxiliary lengthwise cuffing line that prolongs one of the lengthwise cutting lines;
extending the action of one of said lengthwise cuffing tools in order to extend the corresponding lengthwise cutting line into said transition zone between the two successive jobs;
the extended lengthwise cutting line and the auxiliary lengthwise cutting line being joined to one another by said transverse cut.
The various cuts may be made in different sequences along the path of advance of the weblike material. For example, the auxiliary lengthwise cut and the transverse cut may be performed even before the weblike material is cut into strips, in other words upstream of the lengthwise cutting tools, provided that the cut is in the correct position to be able to join up in the desired manner with the lengthwise cuts generated by the cutting tools.
Further advantageous features of the method and of the device according to the invention are indicated in the appended claims.
The invention will be better understood by reading the description that follows with reference to the appended drawings, which show a practical, nonlimiting embodiment of the invention. In the drawings: